The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A216288

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A216288

Prime-free decades such that the next decade is also prime-free.
(history; published version)

#11 by Charles R Greathouse IV at Fri Sep 07 01:09:05 EDT 2012

STATUS

editing

approved

#10 by Charles R Greathouse IV at Fri Sep 07 01:08:54 EDT 2012

COMMENTS

Numbers n such that 10n+1, 10n+3, 10n+7, 10n+9, 10n+11, 10n+13, 10n+17, and 10n+19 are composite. - Charles R Greathouse IV, Sep 07 2012

LINKS

Charles R Greathouse IV, <a href="/A216288/b216288.txt">Table of n, a(n) for n = 1..10000</a>

FORMULA

a(n) ~ n. - Charles R Greathouse IV, Sep 07 2012

PROG

(PARI) is(n)=nextprime(10*n)-10*n>20 \\ Charles R Greathouse IV, Sep 07 2012

(PARI) is(n)=!(isprime(10*n+1) || isprime(10*n+3) || isprime(10*n+7) || isprime(10*n+9) || isprime(10*n+11) || isprime(10*n+13) || isprime(10*n+17) || isprime(10*n+19)) \\ Charles R Greathouse IV, Sep 07 2012

STATUS

approved

editing

#9 by N. J. A. Sloane at Tue Sep 04 14:40:50 EDT 2012

STATUS

editing

approved

#8 by N. J. A. Sloane at Tue Sep 04 14:40:48 EDT 2012

NAME

Prime -free decades such that the next decade is also prime -free.

STATUS

approved

editing

#7 by T. D. Noe at Mon Sep 03 22:16:09 EDT 2012

STATUS

editing

approved

#6 by T. D. Noe at Mon Sep 03 22:16:05 EDT 2012

DATA

113, 133, 134, 167, 218, 248, 314, 323, 347, 374, 418, 430, 476, 484, 512, 524, 536, 545, 560, 575, 596, 640, 650, 674, 692, 708, 713, 726, 737, 776, 797, 833, 839, 847, 848, 890, 907, 935, 944, 956, 998, 1001, 1004, 1037, 1040, 1080, 1081, 1091, 1133, 1175, 1184, 1205, 1212, 1217, 1235, 1286

STATUS

approved

editing

#5 by T. D. Noe at Mon Sep 03 22:15:46 EDT 2012

STATUS

editing

approved

#4 by T. D. Noe at Mon Sep 03 22:15:01 EDT 2012

MATHEMATICA

ps0 = {2, 3, 5, 7}; t = {}; Do[ps1 = Select[Range[10*n, 10*n + 9], PrimeQ]; If[Length[ps0] == Length[ps1] == 0, AppendTo[t, n-1]]; ps0 = ps1, {n, 2, 1000}]; t (* T. D. Noe, Sep 03 2012 *)

STATUS

proposed

editing

#3 by V. Raman at Mon Sep 03 17:23:47 EDT 2012

STATUS

editing

proposed

#2 by V. Raman at Mon Sep 03 16:18:24 EDT 2012

NAME

allocated for V. Raman

Prime free decades such that the next decade is also prime free.

DATA

OFFSET

1,1

CROSSREFS

Cf. A190639, A032352.

KEYWORD

allocated

nonn

AUTHOR

V. Raman, Sep 03 2012

STATUS

approved

editing